We will develop defined culture media in which serum is replaced by a mixture of hormones and other growth factors. These media will be used for establishing and maintaining human tumor cell lines in serum-free conditions. Transplantable human tumors presently being carried in nude mice will be the source of these cell culture lines. We will concentrate on metastatic melanoma, metastatic colon cancer, rectal cancer and epidermal cancer. Previously we have shown that a wide variety of animal cell culture lines can grow in serum-free medium containing classical hormones, growth factors, transport proteins and attachment factors. Such substances and combinations thereof will now be used for the formulation of media suitable for the growth of primary human tumor cell growth of these cells, over, e.g., fibroblasts. Furthermore, these serum-free conditions will reveal hormonal dependence of cells indicative of physiological requirements of the tumors.